Environmental impact of seasonal integrated aquaculture ponds (‘fingerponds\') in the wetlands of Lake Victoria, Kenya: an assessment, with the aid of Bayesian Networks

Abstract

The potential effect on ecosystem integrity of the use of natural wetlands for seasonal wetland fishponds (‘fingerponds\'), integrated with vegetable production for livelihood demands, was evaluated using experimental sites at Lake Victoria, Kenya. Soluble reactive phosphorous and total phosphorus, ammonium, nitrate and total nitrogen data showed no evidence of nutrients leaching from the ponds into the immediate wetland groundwater. Nutrient concentrations in pond water were significantly higher than those in the groundwater in the immediate wetland environment. Bayesian Networks were used to evaluate the main environmental concerns. The environmental impact of fingerponds, particularly on hydrology and biodiversity, was low, although land-use changes at the immediate site where the ponds were dug had direct impacts. Whereas this study was based on short-term monitoring of experimental fingerponds, scaling up of these systems may increase their impact. Continued monitoring is needed during the scaling-up phase.

Keywords: biodiversity, eutrophication, groundwater, hydrology, impact assessment, monitoring, nutrients, scaling-up

African Journal of Aquatic Science 2007, 32(3): 219–234